Whilst in South America in 1833, Darwin traveled on horseback between Patagones and Buenos Aires, visiting a series of “postas”, or staging posts, along the way. He likened the country around one of these to Cottenham Fen, in Cambridgeshire. Interestingly, in his field notebook, he made this comparison in relation to the 6th Posta, whereas when writing up his experiences in his journal, he referred instead to the 7th.
Notebook entry, Monday 16th September 1833: to 6th Posta 5 leagues, road rather better like Cottenham Fen: large graceful soaring flight flocks of glossy Ibis
Journal entry, for the same day: To the 6th Posta; soil black & very soft, generally covered with long coarse herbage; — laborious travelling ... To the 7th Posta, country improving, like Cottenham fen in Cambridgeshire, — a great abundance of beautiful wild fowl.
We can only speculate as to whether Cottenham Fen was one of Darwin's favourite shooting grounds, and whether the “abundance of beautiful wild fowl” in South America brought Cottenham to his mind.